Live Tournament Hand - 66 flopping undercards and open ender

[Honest_Rob]

I called. What's your play on the turn?

230 man $100 buy-in NLHE MTT
Blinds: 200/400
Players left: approx: 160
Average Stack: approx: 4,800-5,000

10 handed
UTG(10,000): calls 400
MP(5,000): calls 400
ME Cutoff(7,500): [6s6d] calls 400
Button(2,300): folds
SB(4,000): folds
BB(10,000): checks

FLOP [3s 4c 5d]
BB: checks
UTG: bets 800
MP: folds
ME Cutoff: calls 800
BB: folds

TURN [3s 4c 5d] [As]
UTG: bets 1200
ME Cutoff: ?